DESCRIPTION (from applicant's abstract) The generation of movements is a fundamental function of the nervous system. It is accomplished by a process, termed motor control, involving the interaction of multiple brain regions. The result of this process is motor commands that encode the appropriate muscle combinations and the timing of their activation for carrying out complex movement sequences. The experiments of this proposal will investigate the interaction of two key motor systems (the motor cortex and the olivocerebellar system) in the generation of these motor commands. The ability of the olivocerebellar system to generate rhythmic synchronous discharges suggests that its function is to bind in time the different muscle groups involved in making complex movement sequences. Indeed, damage to the inferior olive produces motor deficits characterized by the loss of precisely timed muscle activation. Thus, to investigate the interaction of the motor cortex and olivocerebellar system in motor control, whisker movements will be evoked by motor cortex stimuli and the influence of olivocerebellar activity on the evoked movements will be determined. The whisker movements will be recorded using either a photodetector device or high speed video taping. Olivocerebellar activity will be monitored with multiple electrode recordings of complex spike (CS) activity from Purkinje cells, the main target of the olivocerebellar system. Multiple electrode recordings allow determination of the spatial patterns of synchronous CS activity. The first goal will be to demonstrate that there is in fact a significant interaction between these two brain systems: that is that synchronous discharges in the olivocerebellar system gate the efficacy of motor cortex activity in producing movement. The next goal will be to investigate whether the rhythmic nature of olivocerebellar activity allows it to function as an internal clock for organizing motor outputs in time. The third goal will be to determine the major brain sites where the interactions between these systems occur. Finally, the question of whether changes in the patterns of synchronous discharge of the olivocerebellar system result in changes in the pattern of coupling of different muscles will be addressed. In sum, these experiments should help to define the role of the olivocerebellar system in motor control as well as the reasons why cerebellar damage results in motor coordination deficits. They thus represent a step toward the more general goal of understanding cerebro-cerebellar interactions in motor control.